add fmt.Errorf() snippet in UltiSnips

[dastergon]

Hi! I have added an extra snippet to use the 'fe' combination to autocomplete the fmt.Errorf(...) in UltiSnips.

[codecov-io]

Codecov Report

Merging #1677 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1677   +/-   ##
=======================================
  Coverage   22.36%   22.36%           
=======================================
  Files          53       53           
  Lines        4226     4226           
=======================================
  Hits          945      945           
  Misses       3281     3281

Flag	Coverage Δ
#nvim	16.91% <ø> (ø)	⬆️
#vim74	19.4% <ø> (ø)	⬆️
#vim80	21.15% <ø> (ø)	⬆️

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[arp242]

Thanks!